Direct-positive reduction and gold fogged ammoniac silver halide emulsion

ABSTRACT

A direct positive silver halide photosensitive material comprising an ammoniac silver halide photosensitive emulsion and (a) water soluble rhodium salts or water soluble iridium salts, (b) a reducing agent, (c) a gold compound, (d) thiosulfates, thiocyanates, prussic acid salts, and (e) an optical sensitizing dye.

United States Patent Furuya et a1.

[ Feb. 11,1975

DIRECT-POSITIVE REDUCTION AND GOLD FOGGED AMMONIAQS LVER HALIDE EMULSION Inventors: Tetsuo Furuya, Ashigara; Yoshio Ibe; Hideo Kanisawa, both of Odawara, all of Japan Konishiroku Photo Industry Co., Ltd., Tokyo, Japan Filed: June 11, 1973 Appl. No.: 368,868

Assignee:

Foreign Application Priority Data June 17, 1972 Japan 47-60043 US. Cl 1. 96/108, 96/107, 96/101, 196/l 34,96/135,96/137,96/139,96/l32,96/14l Int. Cl G03c l/28 Field of Search 96/108, 101, 120, 107,

[56] References Cited UNITED STATES PATENTS 2,717,833 9/1955 Wark 96/108 2,743,182 4/1956 Lowe et a1.... 96/108 3,445,235 5/1969 Burt 96/101 3,501,307 3/1970 lllingsworth 96/101 Primary Examiner-Norman G. Torchin Assistant Examiner-Won H. Louie, Jr. Attorney, Agent, or FirmBierman & Bierman 6 Claims, No Drawings DIRECT-POSITIVE REDUCTION AND GOLD FOGGED AMMONIC SILVER HALIDE EMULSION This invention relates to direct positive silver halide photosensitive materials and a process for the preparation thereof.

It is well known in the art that when a certain silver halide photosensitive material is employed, a positive image can be directly obatined without employing an intermediate negative medium. However, most of such photosensitive materials are generally very low in the sensitivity.

Among direct positive photosensitive materials, a solarization type photosensitive material is known to have a relatively high sensitivity. In the direct reversal photosensitive material of the solarization type, a silver halide photosensitive material to which a suitable fog has been imparted in advance is employed and a direct positive image is obtained by utilizing the phenomenon of solarization. As a result of extensive research works by Arens et al, it has confirmed that an ammoniac silver bromoiodide emulsion is suitable as the silver halide emulsion of such direct positive photosensitive material of the solarization type.

The fatal defect of this ammoniac silver bromoiodide emulsion is that only a low maximum concentration and only a high minimum concentration are obtained. Various investigations have heretofore been made with a view to improving this defect. For instance, as is disclosed in the specification of U.S. Pat. No. 2,717,833, it has been proposed to incorporate in an ammoniac silver bromoiodide emulsio'in a soluble salt of a group VIII metal, such as a soluble rhodium salt or a soluble iridium salt. However, the direct positive photosensitive amterial according to this proposal is defective in that the contrast is low and a sufficient brightness is not obtained in the high-light portion. Thus, there has not been developed a direct positive silver halide photosensitive material which has a high maximum concentration and a low minimum concentration and which possesses in combination a good contrast and an excellent sensitivity. It is a primary object of this invention to provide a direct positive photosensitive material which is free of the foregoing defects of the conventional direct positive photosensitive material and which has excellent photographic characteristics. v

This invention relates to a direct positive silver halide photosensitive material comprising an ammoniac silver halide emulsion and incorporated therein, (a) at least one compound selected from soluble rhodium salts and soluble iridium salts, (b) a reducing agent, a gold compound, (d) at least 105 mole percent, based on the gold compound, of at least one compound selected from thiosulfates, thiocyanates and prussic acid salts, and (e) and optically sensitizing agent.

It has now been found that excellent photographic characteristics are obtainable by this direct positive silver halide photosensitive material.

As is well known in the art, silver halide emulsions are prepared by the neutral method, the acid method and the ammonia method. As a result of our investigation, it has found that silver halide emulsions prepared by the neutral method of acid method have inevitably some defects. For instance, a spectral sensitization by an optically sensitizing dye is insufficient, or a sufficient sensitivity or high brightness in the low concentration portion is not obtained.

An ammoniac silver halide emulsion to be used in this invention is one prepared by a customary ammonia method. For instance, an ammoniac silver halide emulsion is generally prepared by mixing an aqueous solution of a water-soluble silver salt such as silver nitrate with an aqueous solution of a watersoluble halogen salt such as ammonium bromide and potassium iodide in gelatin or a hydrophilic organic colloid, or with a halogen-saltcontaining, hydrophilic organic colloidal solution. The preparation is conducted in the presence of ammonia, and this ammonia may be in the state incorporated in the silver salt solution or the halogen salt solution. Ammonia may also be in the state incorporated in the hydrophilic colloidal solution, or it may be added separately in the form of an independent solution. As regards the mixing of the silver salt solution and the halogen salt solution, they may beadded simultaneously or separately. Alternately, these solutions are divided into portions, and these divided portions are added in succession. It is also possible to adopt a method in which silver chloride or silver chloride or silver bromide is formed in advance and it is then converted to silver bromide or silver iodide. The foregoing mixing and physical ripening operation is generally carried out at a temperature ranging form 20 to C., preferably from 30 to 50C. The p of the reaction mixture is adjusted above 9, preferably above 11. Ammonia is used in an amount to re-dissolve silver oxide formed when ammonia is added to a water-soluble silver salt solution. This amount is within a range of from 50 to 200 percent, preferably from to percent, based on the silver oxide. A preferable silver halide is silver bromoiodide containing 0.5 to 5 mole percent of silver iodide. It is desired that the average particle diameter of the silver halide is less than 2a, and especially good results are obtained when the average particle diameter of the silver halide is less than 0.6a.

In customary solarization emulsions of the high speed type, the ripening is generally conducted in the presence of excessive silver nitrate or at such a high temperature as ranging from 60 to 80C., or a method of conducting the physical ripening while making present silver chloride having a high solublility is usually adopted.

In this invention, however, such special care need not be taken. This is one of advantages fo this invention.

The soluble rhodium salt or iridium salt to be used in this invention exhibits effects of preventing desensitization owing to kinking and giving a good direct positive image even by high-illuminance, short-time exposure. Preferred examples of the soluble rhodium salt include rhodium halides and hexahalogenorhodates. Preferred examples of the iridium salt include iridium trihalides, iridium tetrahalides, hexahalogenoiridic (III) acids, their sa1ts,'and hexahalogenoiridic (IV) acids and their salts. It is desired that these soluble salts are added to an emulsion at the step of mixing a silver halide (forming an emulsion) or at the step of the physical ripening, and they are added in amounts of 0.001 to 10.0 millimoles per mole of the silver halide.

A suitable fog is imparted to the silver halide emulsion to be used in this invention. The fogging is accomplished by incorporating in the silver halide emulsion a reducing agent and a gold compound and making copresent at least one compound selected from thiocyanates, thiosulfates and prussic acid salts. It is also possible to obtain a good fog when the fogging is effected 3 by a reducing agent and a gold compound in advance and then at least one compound selected from thiosulfates, thiocyanates and prussic acid salts is incorporated in the fogged emulsion.

Reaction conditions for fogging the silver halide may be varied within'a broad range. The P is generally adjusted within a range of 5.5 to 9, preferably 6 to 7. Further, the PAg is generally within a range of 6.5 to 8.5, and the temperature is generally adjusted to 40 to 100C., preferably 50 to 75C. The hydrophilic protective colloid for suspending the silver halide particles during the fogging treatment, such as gelatin, is used preferably in an amount of 30 to 200g per mole of the silver halide.

As the reducing agent, there are conventiently used aldehyde compounds such as formalin, organic amines such as hydrazine, triethylene tetramine, thiourea dioxide and imino-amino-methane-sulfonic acid,and other organic reducing agents. In addition, inorganic reducing agents such as stannous chloride and such reducing agents as amine borane are also conveniently used. The concentration of the reducing agent used is changed depending on the silverhalide particle size, the kind of the silver halide, the intended use and other factors, and it differs also depending on eht kind of the reducing per se. In general, however, the reducing agent is used in an amount of 0.001 to l millimoles per mole of the silver halide.

As the gold compound to be used in this invention, there maybe mentioned soluble salts of monovalent or trivalent gold, such as chloroauric acd, gold thiocyanate, sodium chloroaurate, potassium aurate, potassium chloroaurate, potassium gold cyanide, potassium bromaurate, potassium iodoaurate, potassium gold thiocyanide, sodium gold thiomaleate, gold thioglucose and the like.

The amount used of the gold compound is changed depending on the size of the silver halide particles, the composition of the silver hlide and the intended use, but it is generally used in an amount of 0.0001 to 0.1 millimoles, preferably 0.005 to 0.5 milliomoes, per mole of the silver halide. Good results are obtained when the gold compound is used at such a low concentration.

in this invention, as the thiosulfate, thiosulfate, thiocyanate and prussic acid salt, there are preferably used sodium thiosulfate, potassium thiocyanate, ammonium thiocyanate, potassium cyanide, sodium cyanide, and complex salts thereof. Such compound is generally used in an amount of 0.0003 to 100.0 millimoles, pref erably 0.01 tolO millimoles per mole of the sliver halide.

It is indispensable, however, that such compound is used in an amount of at least 105 mole percent based on the gold compound. Addition of these thiosulfates, thiocyanates and prussic acid salts may be effected prior to the fogging by the reducing agent and gold, during the fogging operation or after formation of fog. However, the amounts of such compounds are changed depending on the time of addition, and when they are added after formation of fog, it is necessary to increase their amounts.

The ratio of the gold compound and reducing agent used for imparting fog to the silver halide emulsion varies depending on various factors, but optimum results are generally obtained when said ratio is within a range of l 3 to l 200 (on the weight basis).

The optically sensitizing dye to be used in this invention is selected from optically sensitizing dyes customarily used for ordinary negative type silver halide emulsions. For instance, cyanines, merocyanines, pseudocyanines, hemicyanines and the like are generally used. Although it has been known in the art to employ these optically sensitizing dyes for direct positive photographic emulsions, they are generally defective in that they cause excessive softening. Accordingly, the specification of British Pat. No. 970,601 proposes indocyanines as optically sensitizing dyes free of-softening, and Japanese Patent Publication No. 1 1623/7] teaches that sufficient results cannot be obtained by use of such indocyanine alone, and it proposes a method using, in combination with such indocyanine, a bis-thiazolyl or selenazolyl compound.

In contrast to such convention al techniques, in this invention, such extreme softening as caused when an ordinary sensitizing dye is added to a direct positive emulsion is not at all observed, and in the case of some optically sensitizing dyes, high contrast is rather observed.

Dyes to be used especially preferably in this invention are cyanine dyes expressed by the following general formula (I) wherein Z and Z stand for an atomic group necessary for formation of a heterocyclic ring, m is l or 2 with the proviso that when m is 1, Z, is a 2-quinoline ring, R and R stand for an alkyl group, R designates a hydrogen atom or an alkyl group, X is an anionic group, and n is l or 2, and merocyanine dyes expressed by the following general formula (ll) Wherein Z stands for a non-metallic atomic group necessary for formation of a heterocyclic ring, R R and R stands for an alkyl, alkenyl or aryl group, R designates a hydrogen atom or an alkyl or aryl group, I and dare I or2,andpis 1,2or3. It is possible to employ these cyanine or merocyanine dyes in the form of admixtures of two or more of them. In the optically sensitizing dyes expressed by the above general formulae, the heterocyclic ring is preferably a 85- or 6 -membered ring. For instance, there are preferably used atomic groups necessary for formation of thiazole type nuclei (such as thiazole, 4- methylthiazole, 4-phenylthiazole and 4,5- diphenylthiazole), benzothiazole type nuclei (such as benzothiazole, S-chlorobenzothiazole, 5- methylbenzothiazole, 6-methylbenzothiazole, 5- V phenylbenzothiazole, 5-methoxybenzothiazole, 6-

ethoxybenzothiazole, S-hydroxybenzothiazole, tetrahy droxybenzothiazole, 5,6-dimethoxybenzothiazole and 5,6-dioxymethylene benzothiazole), naphthothiazole type nuclei (such as L -naphthothiazole, -napnthothiazole and, naphthothiazole), oxazole type nuclei (such as 4-methyloxazole, 4-phenyloxazole and 4,5- diphenyloxazole), benzoxazole type nuclei (such as benzoxazole, S-chlorobenzoxazole, 5- methylbenzoxazole, S-phenylbenzoxazole, 6- methylbenzoxazole, 5,6-dimethyl benzoxazole and 5- methoxybenzoxazole), naphtoxazole type nuclei (such as a-naphthoxazole, B-naphthoxazole and [MT-naphthoxazole), selenazole type nuclei (such as 4- methylselenazole and 4-phenylselenazole), benzoselenazole type nuclei (such as benzoselenazole, 5- chlorobenzoselenazole, S-methylbenzoselenazole, 5- chlorobenzoselenazole, S-methylbenzoselenazole, 5- methoxybenzoselenazole and tetrahydrobenzoselenazole), naphthoselenazole type nuclei (such as (at-naphthoselenazole and B-naphthoselenazole), thiazoline type nuclei (such as thiazoline and 4- methylthiazoline), oxazoline type nuclei (such as oxazoline and 4-methloxazoline), pyrroline type nuclei (such as oxazoline and 4-methloxazoline), pyrroline type nuclei (such as pyrroline, 4-methylpyrr0line, 5- methylpyrroline and 4-phenylpyrroline), 3,3- dialkylindolenine type nuclei (such as 3,3- dimethylindolenine, 3,3,S-trimethylindolenine and 3,3- dimethyl 5-chloroindolenine), l,l-dialkylbenzoindolenine type nuclei (such as 1,1-dimethylbenz (e) indolenine and l,l-dimethyl (g) indolenine), 1- alkylbenzimidazole, l-alkyl 5,6-dichlorobenzimidazole and l-aryl--chlorobenzimidazole), naphthimidazole type nuclei (such as l-alkyl 2-naphthimidazole and lalkyl-B-naphthimi dazole,), and pyridine type nuclei (such as Z-quinoline, 6-methyl-2-quinoline, 6-methoxy- 2-quinoline, 4-quinoline and 8-chloro-4-quinoline).

In the case of cyanine dyes, thiazole, benzothiazole and benzoselenazole nuclei are especially preferred, and as the alkyl group, methyl, ethyl, sulfopropyl, sulfobutyl, sulfate-propyl, carboxymethyl, carboxyethyl and hydroxyethyl groups are preferred. Further, phenyl, sulfophenyl, carboxyphenyl. tolyl and chlorophenyl groups are preferred as the aryl group, and an allyl group is preferred as the alkenyl group.

Furthermore, dyes exhibiting a drastic desensitizing effect in ordinary negative type silver halide emulsions, such as cyanines and merocyanines having such a desensitizing effect in ordinary negative type silver halide emulsions, such as cyanines and merocyanines having such a desensitizing nucleus as imidazoquinoxaline,

pyrazole, indole and pyrrolopyrido nuclei or having such a desensitizing substituent as a No. 2 group stituent may be used in combination with the foregoing optically sensitizing dyes in this invention.

5 It is also possible to employ a fluoresenct witening agent expressed by the following general formula (III) Wherein M stands for a hydrogen atom or a cation, or a fluorescent whitening agent having an analogous structure as a super-sensitizing agent in combination with the optically sensitizing dye.

The optically sensitizing dye may be incorporated in the photosensitive material according to customray procedures. For instance, the optically sensitizing dye is dissolved into a suitable solvent such as water, methanol and ethanol, and the solution is added, preferably, to the emulsion. The dye is used in an amount of about 1 mg to about 300 mg per liter of the emulsion.

As preferred examples of the optically sensitizing dye, there may be mentioned the following compounds:

S S 2 \GH2 cn CH Ca 1 c n 'CZH5 l I 5 CH5 3,865,596 7 11 v l 12 (35) Among these optically sensitizing dyes, cycnine dyes exhibit especially excellent photographic characteris- N tics when they are used in combination with the aboveo l mentioned fluorescent whitening agents.

ON In this case, the fluorescent whitening agent is used l preferably in an amount of about 1() mg to about l() g CH GI-F per liter of the emulsion.

Further, in the case of merocyanine dyes, when the above illustrated meroeyanine dyes (12) to (27) are m used in combination with the above illustrated merocyanine dyes (28) to (35 there is attained an effect of C S preventing the desensitization frequently caused by res- 0 idence of the emulsion observed when the emulsion is kept still for long time at a coating temperature. CH 0H 0H In this case, it is desired that the merocyanine dye of 2 2 5 the former type and that of the latter type are used in I combination at a weight ratio of from 1 10 to 10 l. as H O S In addition to the foregoing ingredients, other'photographic additives may be incorporated in the direct N/ c S positive silver halide emulsion of this invention. 2 l (.7 =5 For instance, the direct positive silver halide emul- C sion of this invention may comprise as a stabilizer a CH I polymer compound having in the molecule a group ex- GHZCHZSOSH pressed by the following formula (IV) s 1) CH R r 10 N l c-- s l l g 30 A coo-r'q-n Wherein A designates a hydrogen atom or a group -CooM (in which M, is

"an s @(N G==Ts s g .5 10

N C: -I lH-R O: 11 2 5 GH SO H-N(G H 5 or other cation), R is a hydrogen atom or a methyl j j N w A group, or a group-CH COOM (only when A is hydrogen atom), R is an lakyl group or a hydroxyl-or phenylsubstituted alk l grou and R and R stand for a h 4s y P y ig g r drogen atom, an alkyl group or a hydroxyl-substituted 0' alkyl group, or they may form a ring. a compound ex- Hz CH OH pressed by the following formula (V) N C: S

g H O(CH) ca SOM l 0 ,f 2 y 3 @2115 12 2 5 Wherein Y is O or an integer of from I to 8, R is a m 2 2 hydrogen atom, an alkyl or arylgrouphaving up to l7 o I carbon atoms, and M is a cation, a trlazole, an azalndene, a quarternary benzothiazolium compound, or a water-soluble inorganic salt of cadmium, cobalt, man- 7 ganese or zinc. The emulsion may further comprise a H g 0 f 7 6O filmhardner such as formalin, mucochloric acid, chro- 5 mium alum, glyoxazole and dibromoacrolein; a gelatin plasticizer such as a compound expressed by the fol- SO NI- lowing formula (VI) 440 O (N-CHZCH CO) (N-CH ca co) L;,l 1: =0H *GH G S l bl l 2 2 a N (CH2) 33 I 2) C1 l 0:0 l I on wherein c and stand for an integer of from 2 to V 5, b, and [1 stand for a positive integer, glycerine, a dihydroxyalkane, ethylene, a bis-glycolic acid ester and an acid amide of the acrylic acid of the acrylic acid yp a film property-improving agent such as a polymer latex obtained by grafting an unsaturated ethylenic monomer to a hydroxyl group-containing polymer compound with use of a secondary cerium salt, and a polymer latex of an unsaturated ethylenic monomer formed with use of an activating agent expressed by the following formula (VI) wherein R is a alkyl having carbon atom from 4 to 8 or C 18 alkyl substituted alyl, B is divalent chainkydrocarbon radical M is cation atom, e is a positive integer of from 1 to 50, a coating assistant such as saponin, a lauryl or oleyl monoether or polyethylene glycol and an amylated alkyl taurine; a sensitizer such as polyalkyleneoxide and its derivatives, potassium bromide, potassium iodide and other soluble halogen salts; a coupler such as -pyrazolone couplers, phenolic couplers, naphtholic couplers and couplers having an active methylene group inserted between two carbonyl groups; and a liquor obtained by dissolving a main developer such as methylhydroquinone dimethyl ester and phenylhydroquinone in a high-boiling-point solvent and dispersing the solution into an aquieous solution of gelatin, and a liquor obtained by dispersing protectively a tannin developer such as 3,4- dihydroxydiphenyl and 2.5-dihydroxydiphenyl. These additives are added at an appropriate stage during the preparation of the emulsion.

The so obtained direct reversal silver halide emulsion is coated and dried on a suitable support according to a customary method, if necessary, after a suitable hydrophilic treatment such as an undercoating treatment, has been conducted.

As the support there may be exemplified a paper, an olefin resincoated paper, glass, cellulose acetate, cellulose nitrate and a film of a synthetic resin such as polyester, polyamide, polystyrene and the like.

The so obtained direct positive silver halide photosensitive material of this invention is used in various fields of the photographic art. For instance, in the field of printing, it is used for duplicating films, reproduction films, offset masters and the like. Furhter, in the general field, it is used as a direct positive photosensitive material for reproduction, microfilm, direct color positive, quick stabilization, diffuse transfer, color diffuse transfer and mono-bath development. Kinds of the photographic additive and silver halide and the preparation conditions are appropriately chosen depending on such uses.

The direct positive silver halide photosensitive material of this invention having the above-mentioned structure has excellent photographic characteristics such as a high contrast, a low minimum concentration, a high maximum concentration, a high maximum concentration, a high sensitivity and other improved properties, and the defects of the conventional direct positive photosensitive materials can be overcome by the photosensitive material of this invention.

As will be apparent from Examples given hereinafter, such excellent photographic characteristics are at tained by synergistic effects of an ammoniac silver halide emulsion with (a) at least one compound selected from soluble rhodium salts and soluble iridium salts, (b) a reducing agent, (0) a gold compound, (d) at least 105 mole percent, based on the gold compound, of at least one compound selected from thiosulfates, thiocyanates and prussic acid salts and (e) an optically sensitizing agent. If any one of the foregoing ingredients is not incorporated, unsatisfactory results alone are obtained. It is considered that the combination of these ingredients emphasizes effects attained by single use of each ingredient and yields excellent effects unobvious over the single use of each ingredient, with the result that excellent photographic characteristics can be ob tained.

This invention will now be illustrated more detailedly by reference to Examples, but embodiments of this invention are not limited to those illustrated in these Examples.

Example 1 An ammoniac silver bromoiodide emulsion containing a rhodium salt and comprising a silver bromoiodide having an average particle diameter of about 0.3 p. and containing about 1.4 mole percent of silver iodide was prepared in the following manner [emulsion (1)].

a) gelatin 48 g water 480 cc b) Silver nitrate 96 g water 300 cc c) potassium bromide 68 g potassium iodide 1.28 g rhodium lrichloride 24 mg 28% aqueous ammonia ct: water 92 cc d) sulfuric acid amount sufficient to to neutralize the emulsion to a pH value of 5.0

The liquor b) was added to the liquor a) at 40c. and the liquor c) was further added under ripened. Then, the ripening was conducted at 40C. for 5 minutes and the liquor d) was added to neutralize the emulsion to a P value of 5.0. The emulsion was desalted, and there was obtained 1200 cc of a final emulsion. As comparative emulsions, emulsion (ll) was prepared in the same manner as described above except that rhodium chloride was not added, and emulsion (III) comprising a silver bromoiodide having the same average particle size and the same silver halide composition and containing the same amount of rhodium chloride as described above was prepared by the neutral method.

Each emulsion was adjusted to P of 6.8 and PAg of 7.5, and 3.5 milligrams of tetraethylene pentamine was added to effect the ripen at 60C. for 30 minutes.

Then, the resulting emulsion was divided into 2 portions, and 0.5 milligram (a) of chloroauric acid was added to one portion and 2.5 milligrams (b) of chloroauric acid was aged at 60c. until appropriate fog was obtained.

The so ripened emulsion was cooled and further divided into portions. These portions were treated under conditions indicated in Table 1. Into each emulsion was incorporated 5- (3-ethyl-2-benzothia-zolinilidene)-3- ethyloxazolidione in amount of mg per mole of silver. t

Then, a spreader and a filmhardening agent were further incorporated into the emulsion, and it was coated and dried on a film base in an amount of 4 g, calculated as silver, per square meter of the film.

Each of the so obtained samples was subjected to an optical wedge for sensitiometry and exposed to light emitted from a tungsten light source. The development was conducted according to customary procedures to obtain results shown in Table l.

D-72 type developer (recipe by Eastman Kodak Co.) was used for the development.

corporated with -(3-ethyl-2-benzothiazolinidene) -3- propylrhodanine in an amount of 100 mg per mole of silver.

The emulsion was then incorporated with a spreader and a film-hardening agent and coated on a film base in an amount of 4g, calculated as silver, per square meter of the film. The so obtained samples were treated in the same manner as described in Example 1, to obtain results shown in Table 2.

TABLE 1 Emulsion Pinacryptol S202, CNS or CN Compound Amount Added Sensitivity* Minimum amma yellow (mg/mol Ag) Value Concentration mg Sodium 35 380 4.2 0.05 thiosulfate 175 5 00 4.7 0.03 la not added potassium 410 4.3 0.03 cyanide 75 630 5.2 0.02 Ammonium 200 3.3 0.07 thiocyanate 175 260 3.7 0.05

15 1.5 0.17 Sodium 35 290 3.8 0.07 thiosulfate 175 380 4.1 0.04 lb not added Potassium 15 355 4.0 0.04 cyanide 75 480 4.7 0.03 Ammonium 35 65 2.1 0.12 thiocyanate 175 110 2.7 0.08

lla not added 5.32 Sodium thiosulfate 175 5.16

[lb not added Sodium thiosulfate 175 5.30

Ila 350 mg 25 2.5 0.08 350 mg Sodium thiosulfate 175 4.0 0.03

[lb 350 mg Sodium thiosulfate 175 3.7 0.04

"In not added 1.9 0.06 Sodium thiosulfate 175 1 10 2.8 0.03

lllb not added 10 1.1 0.10 Sodium thiosulfate 175 2.6 0.05

Each sample exhibited a maximum concentration ex- Table 2 ceeding 5.0.

From the practical viewpoint, a reciprocal number of 45 Chloroauric Ammonium Rela- Minimum MaXi:

amma mum the amount exposedof l1ght necessary for destroymg Add Thiosulfate five value Concen Concem the fog under wh1te light exposure unt1l the concentra- (m. mole/ (mole %/Au Speed tration tration tion reached 0.2 was calculated, and the sensitivity in Ag (Impound) the Table was expressed in terms of a relative speed. 0005 25 O. From the results shown 1n the Table, 1t 1s seen that 0.005 100 100 2.6 0.10 5.0 0005 29 007 50 each of samples accordmg to th1s 1nvent1on had excel- 0005 150 255 lent photographic characteristics such as a high speed, 05 30 3 4,3 ()3 50 a i rast and i hbri ht ss at the] wconcen- 35 h com a h g g o 0.015 100 38 1.7 0.10 5.0 "anon p 0.015 105 70 2.0 0.9 5.0 55 0.015 150 2.7 0.07 5.0 Example 2. 0.015 300 300 3.8 0.04 5.0

According to the recipe of the emulsion (I) of Example 1, an ammoniac silver bromoiodide emulsion was prepared. After completion of the physical ripening, the desalting was carried out, and P and PAg were adjusted to 6.8 and 7.5, respectively. Then, triethylene tetramine was added in an amount of 4.0 mg to the emulsion, and the ripening was effected at 65C. for 30 minutes. The emulsion was divided into several portions, and ammonium thiosulfate was added into the divided portions in amounts indicated in Table 2, and the ripening was conducted at 65C. for 5 minutes Then, chloroauric acid was added and the ripening was carried out until a suitable fog was obtained. 0

Each of the so ripened emulsions was cooled and in- As is seen from the results shown in Table 2, in case ammonium thiosulfate was added in an amount of at least 105 mole percent based on the gold compound, the increase of the relative speed and the increase of the gamma value were observed.

Example 3 Table 4 Emulsion (B) Amount Added Relative Speed Relative Speed Minimum amma Illustrative of dye under white under yellow value concendye (mg/mol Ag) light exposure light exposure tration not added I I00 2.4 0.l2 (33) I20 I10 580 2.0 0.14 (38) 120 I00 500 L9 014 (I4) I00 I80 2,790 1.8 0.l5 (20) I00 200 2,950 1.6 0.16 (23) I00 ll0 I,I50 1.6 0.15 (39) I00 75 650 1.3 0.21 (40) I00 I05 1.040 l.7 0.18 (25) 50 40 260 l.l 0.23 (2) I00 200 L830 1.9 0.14 (I0) I00 I00 900 2.1 0.l5 (I2) I00 160 1,550 2.0 015 (I3) I00 I20 700 L) 0.17

a) Gelatin 50 g As is apparent from the results shown in Table 3 and potassium hexachloro- 50 mg 4, the samples according to this invention (samples pre- IOOU Cc pared from the emulsion (A) had excellent photob) 200 g 20 graphic characteristics. Namely, they had a low mini- 28% flquefiusflmmfinifl CC mum concentration and a high maximum concentra- WZIKCT Cc M potassium iodide 140 g tron as well as a high gamma value.

potassium iodide g water 1000 cc What IS Claimed is: d) glacial acetic acid amount sufficient to neutralize the emulsion to a p value of 5.5

The liquor b) was added to the liquor a) at 38C. and the liquor c) was further added under ripening. The, the ripening was carried out at 38C. for 10 minutes, and the liquor d) was added to neutralize the emulsion to a P value of 5.5.

The emulsion was desalted, and 50 g of preparation acid and was further ripened at 60C. for 40 minutes to' impart a fog to the emulsion. The portion (B) was incorporated with I mg of formalin and ripened at 60C. for 60 minutes. Then, 1.5 mg of chloroauric acid was added to the emulsion and ripening was carried out at 60C. for 40 minutes to impart a fog to the emulsion. The so obtained emulsions were divided into portions and these portions were incorporated with optically sensitizing dyes indicated in Tables 3 and 4. Then, a spreader and a film-hardener were added to each emulsion and the emulsion was coated on a film base in an amount of 3.5 g, calculated as silver, per square meter of the film.

The so obtained samples were treated in the same manner as described above to obtain results shown in l. A direct positive silver halide photosensitive material comprising an ammoniac silver halide photosensitive emulsion and(a) at least one compound selected from soluble rhodium salts and soluble iridium salts, said compound having been incorporated into said emulsion in an amount of 0.001 to 10 millimoles per mole of the silver halide before or at physical ripening, (b) a reducing agent in an amount of 0.001 to 100 millimoles per mole of the silver halide, (c) a gold compound in an amount of 0.0001 to 0.1 millimoles per mole of the silver halide, (d) at least I05 mol percent, based on said gold compound, of at least one compound selected from thiosulfates, thiocyanates, prussic acid salts, and (e) an optical sensitizing dye, said reducing agent and said gold compound being present in sufficient amounts to cause fogging of said silver halide.

2. A direct positive silver halide photosensitive material according to claim 1, wherein said silver halide emulsion comprises a silver bromoiodide containing 0.5 to 5 mol percent of silver iodide.

3. A direct positive silver halide photosensitive material according to claim 1, wherein the weight ratio of said gold compound to said reducing agent is from l:3 to 1:200.

4. A direct positive silver halide photosensitive mate- Tab1e 3 and 4 na] according to claim 1, whereln said sensitizing dye Table 3 Emulsion (A) Amount Added Relative speed Relative speed Gamma Minimum Illustrative of dye under white under yellow Value concendye (mg/mole Ag) light exposure light exposure trationnot added I00 I00 4.3 0.04 (33) I20 300 4.000 4.5 0.04 (38) I20 I 2,700 4.3 0.04 I4) I00 520 20,000 4.8 0.03 (20) I00 570 27.600 5.l 0.03 (2 3) I00 495 I0.0ll0 4.4 0.04 (39) I00 260 8,400 3.8 0.05 (40) I00 200 (1,230 4. I 0.06 (25) 50 55 1,440 3.| 0.06 (2) I00 400 11.980 4.3 0.05 I0) I00 I80 2,000 4.5 0.05 (I2) I00 340 6,820 4.7 0.06 (13) I00 2I0 3,500 4.3 0.06

is selected from sensitizing dyes represented by the following general formula (I) or (ll):

wherein Z and Z stand for an atomic group necessary for formation ofa heterocyclic ring, m is l or 2 with the proviso that when m is 1, Z, is a 2-quinoline ring, R and R stand for an alkyl group, R designates a hydrogen atom or an alkyl group, X is an anionic group, and n is l or 2,

nv '8 I s 1 wherein Z stands for a non-metalic atomic group necessary for formation of a heterocyclic ring, R R and R individually stand for an alkyl, alkenyl or an aryl group, R designates a hydrogen atom or an alkyl or aryl t cu cu) :c =(cH 0). W1

group, I and d are individually l or 2, and p is l, 2 or 3.

rial according to claim 1, wherein said reducing agent is selected from formalin, hydrazine, triethylene tetramine, thiourea dioxide, imino-amino-methane-sulfonic acid, stannous chloride and amine borane. 

1. A DIRECT POSITIVE SILIVER HALIDE PHOTOSENSITIVE MATERIAL COMPRISING AN AMMONIAC SILVER HALIDE PHOTOSENSITIVE EMULSION AND(A) AT LEAST ONE COMPOUND SELECTED FROM SOLUBLE RHODIUM SALTS AND SOLUBLE IRIDIUM SALTS, SAID COMPOUND HAVING BEEN INCOPORATED INTO SAID EMULSION IN AN AMOUNT OF 0.001 TO 10 MILLIMOLES PER MOLE OF THE SILVER HALIDE BEFORE OR AT PHYSICAL RIPENING, (B) A REDUCING AGENT IN AN AMOUNT OF 0.001 TO 100 MILLIMOLES PER MOLE OF THE SILVER HALIDE, (C) A GOLD COMPOUND IN AN AMOUNT OF 0.0001 TO 0.1 MILLIMOLES PER MOLE OF THE SILVER HALIDE, (D) AT LEAST 105 MOL PERCENT, BASED ON SAID GOLD COMPOUND, OF AT LEAST ONE COMPOUND SELECTED FEOM THIOSULFATES, THIOCYANTES, PRUSSIC ACID SALTS, AND (E) AN OPTICAL SENSITIZING DYE, SAID REDUCING AGENT AND SAID GOLD COMPOUND BEING PRESENT IN SUFFICEINT AMOUNT TO CAUSE FOGGING OF SAID SILVER HALIDE.
 2. A direct positive silver halide photosensitive material according to claim 1, wherein said silver halide emulsion comprises a silver bromoiodide containing 0.5 to 5 mol percent of silver iodide.
 3. A direct positive silver halide photosensitive material according to claim 1, wherein the weight ratio of said gold compound to said reducing agent is from 1:3 to 1:200.
 4. A direct positive silver halide photosensitive material according to claim 1, wherein said sensitizing dye is selected from sensitizing dyes represented by the following general formula (1) or (II):
 5. A direct positive silver halide photosensitive material according to claim 1, which comprises said thiosulfates, thiocyanates and/or prussic acid salts being present in an amount of 0.003 to 100 millimoles per mole of the silver halide.
 6. A direct positive silver halide photosensitive material according to claim 1, wherein said reducing agent is selected from formalin, hydrazine, triethylene tetramine, thiourea dioxide, imino-amino-methane-sulfonic acid, stannous chloride and amine borane. 